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Relative Importance of Different Water Categories as Sources of N‑Nitrosamine Precursors Teng Zeng,†,‡,∥,∇ Caitlin M. Glover,§,∇ Erica J. Marti,§ Gwen C. Woods-Chabane,§,⊥ Tanju Karanfil,# William A. Mitch,*,†,‡ and Eric R. V. Dickenson*,§ †
Department of Civil and Environmental Engineering, Stanford University, 473 Via Ortega, Stanford, California 94305, United States National Science Foundation Engineering Research Center for Re-Inventing the Nation’s Urban Water Infrastructure (ReNUWIt), 473 Via Ortega, Stanford, California 94305, United States § Water Quality Research and Development Division, Southern Nevada Water Authority, Henderson, Nevada 89015, United States ∥ Department of Civil and Environmental Engineering, Syracuse University, 151 Link Hall, Syracuse, New York 13244, United States ⊥ HDR, Inc., 431 W Baseline Road, Claremont, California 91711, United States # Department of Environmental Engineering and Earth Sciences, Clemson University, 342 Computer Court, Anderson, South Carolina 29625, United States ‡
S Supporting Information *
ABSTRACT: A comparison of loadings of N-nitrosamines and their precursors from different source water categories is needed to design effective source water blending strategies. Previous research using Formation Potential (FP) chloramination protocols (high dose and prolonged contact times) raised concerns about precursor loadings from various source water categories, but differences in the protocols employed rendered comparisons difficult. In this study, we applied Uniform Formation Condition (UFC) chloramination and ozonation protocols mimicking typical disinfection practice to compare loadings of ambient specific and total N-nitrosamines as well as chloramine-reactive and ozone-reactive precursors in 47 samples, including 6 pristine headwaters, 16 eutrophic waters, 4 agricultural runoff samples, 9 stormwater runoff samples, and 12 municipal wastewater effluents. N-Nitrosodimethylamine (NDMA) formation from UFC and FP chloramination protocols did not correlate, with NDMA FP often being significant in samples where no NDMA formed under UFC conditions. N-Nitrosamines and their precursors were negligible in pristine headwaters. Conventional, and to a lesser degree, nutrient removal wastewater effluents were the dominant source of NDMA and its chloramine- and ozone-reactive precursors. While wastewater effluents were dominant sources of TONO and their precursors, algal blooms, and to a lesser degree agricultural or stormwater runoff, could be important where they affect a major fraction of the water supply.
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N-nitrosamines on the draft Contaminant Candidate List 410 and is evaluating whether to regulate N-nitrosamines.11 The World Health Organization (WHO) has established a 100 ng/L guideline value for NDMA.12 Research has attempted to identify specific NDMA precursors by evaluating NDMA yields from model compounds.5,13 Upon chloramination, secondary, tertiary and quaternary amines form NDMA, with yields following the general order of secondary ≥ tertiary > quaternary.14,15 However, a subset of tertiary amines with β-aromatic substituents exhibit the highest NDMA yields.16−18 Amidecontaining compounds, featuring secondary or tertiary amine moieties attached to carbonyl or thionyl groups, also form
INTRODUCTION Water utilities have been evaluating utilization of impaired source waters,1 such as those impacted by upstream wastewater discharges,2 to expand water supplies. Many U.S. utilities also are switching from chlorination to chloramination to limit the formation of halogenated disinfection byproducts (DBPs; e.g., trihalomethanes and haloacetic acids) to comply with the Stage 2 Disinfectants and Disinfection Byproducts Rule.3 Some utilities are considering incorporating ozone pretreatment to enhance pathogen inactivation and organic contaminant removal.4 Unfortunately, both chloramination and ozonation can promote N-nitrosamine formation.5 N-Nitrosodimethylamine (NDMA) is the most frequently detected N-nitrosamine in drinking water,6,7 with a 0.6 ng/L concentration associated with an age-adjusted 10−6 lifetime excess cancer risk.8 The California Department of Public Health has established a 10 ng/L Notification Level for three N-nitrosamines, including NDMA,9 while the USEPA has included NDMA and four other © 2016 American Chemical Society
Received: Revised: Accepted: Published: 13239
September 13, 2016 November 3, 2016 November 7, 2016 November 7, 2016 DOI: 10.1021/acs.est.6b04650 Environ. Sci. Technol. 2016, 50, 13239−13248
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Environmental Science & Technology NDMA at lower yields.19,20 Upon ozonation, compounds bearing hydrazine, sulfamide, hydrazone, and carbamate moieties form NDMA.21−24 Many of these structures occur in pharmaceuticals (e.g., ranitidine)18 and personal care products (e.g., shampoos),14 pesticides (e.g., diuron),19 cationic coagulation polymers25 and anion exchange resins.26,27 However, beyond water treatment chemicals (e.g., cationic coagulation polymers), demonstration of the importance of specific precursors to NDMA formation in authentic source waters has been limited to antiyellowing agents21,22 or the fungicide, tolylfluanide,24 as NDMA precursors during ozonation, or methadone as a NDMA precursor during chloramination.28 Furthermore, although NDMA is the most prevalent of specific N-nitrosamines detected in drinking waters or wastewaters, it represents a small fraction ( baseline eutrophic water (EW) > headwater (HW). We estimated the volumetric proportion of source waters in a headwater that could account for a given level of NDMA or TONO formation, assuming that the headwater is only impacted by a single source. For a water to produce the 10 ng/L NDMA California Notification Level upon UFC chloramination (more realistic conditions as compared to FP conditions), the volume fraction of a conventional and nutrient removal wastewater effluent in the headwater has to reach ∼5% and 35%, respectively, while even 100% of other source waters could not generate this NDMA level. These fractions were calculated by dividing 10 ng/L by the median NDMA concentration measured for each water category, assuming negligible NDMA formation in the headwater. Similarly, for an impaired headwater to form TONO at 100 ng/L as NDMA (targeted assuming NDMA constitutes 10% of TONO29,30) upon UFC chloramination, the volume fraction of an agricultural runoff, stormwater runoff, algal-impacted eutrophic 13245
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Environmental Science & Technology
(2) Rice, J.; Westerhoff, P. Spatial and temporal variation in De Facto wastewater reuse in drinking water systems across the U.S.A. Environ. Sci. Technol. 2015, 49 (2), 982−989. (3) Seidel, C. J.; McGuire, M. J.; Summers, R. S.; Via, S. Have utilities switched to chloramines? J. Am. Water Works Assoc. 2005, 97 (10), 87−97. (4) Gerrity, D.; Pisarenko, A. N.; Marti, E. J.; Trenholm, R. A.; Gerringer, F.; Reungoat, J.; Dickenson, E. R. V. Nitrosamines in pilotscale and full-scale wastewater treatment plants with ozonation. Water Res. 2015, 72, 251−261. (5) Krasner, S. W.; Mitch, W. A.; McCurry, D. L.; Hanigan, D.; Westerhoff, P. Formation, precursors, control, and occurrence of nitrosamines in drinking water: A review. Water Res. 2013, 47 (13), 4433−4450. (6) Woods, G. C.; Dickenson, E. R. V. Evaluation of the final UCMR2 database: Nationwide trends in NDMA. J. Am. Water Works Assoc. 2015, 107 (1), E58−E68. (7) Russell, C. G.; Blute, N. K.; Via, S.; Wu, X.; Chowdhury, Z. Nationwide assessment of nitrosamine occurrence and trends. J. Am. Water Works Assoc. 2012, 104 (3), 57−58. (8) U.S. Environmental Protection Agency; Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water Contaminant Candidate List; U.S. Environmental Protection Agency: Washington, DC, 2014. https://federalregister. gov/a/2014-24582 (accessed November 1, 2016). (9) California Department of Public Health; NDMA and Other Nitrosamines - Drinking Water Issues; California Department of Public Health: Sacramento, CA, 2013. http://www.waterboards.ca.gov/ drinking_water/certlic/drinkingwater/NDMA.shtml (accessed November 1, 2016). (10) U.S. Environmental Protection Agency; Draft Contaminant Candidate List 4-CCL 4; U.S. Environmental Protection Agency: Washington, DC, 2015. http://www.epa.gov/ccl/chemicalcontaminants-ccl-4 (accessed November 1, 2016). (11) U.S. Environmental Protection Agency, Office of Water; A New Approach to Protecting Drinking Water and Public Health; U.S. Environmental Protection Agency: Washington, DC, 2010. https:// nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1006RG2.TXT (accessed November 1, 2016). (12) World Health Organization (WHO); Guidelines for DrinkingWater Quality, 3rd ed.; World Health Organization: Geneva, Switzerland, 2008. http://www.who.int/water_sanitation_health/ dwq/fulltext.pdf (accessed November 1, 2016). (13) Shah, A. D.; Mitch, W. A. Halonitroalkanes, halonitriles, haloamides, and N-nitrosamines: A critical review of nitrogenous disinfection byproduct formation pathways. Environ. Sci. Technol. 2012, 46 (1), 119−131. (14) Kemper, J. M.; Walse, S. S.; Mitch, W. A. Quaternary amines as nitrosamine precursors: A role for consumer products? Environ. Sci. Technol. 2010, 44 (4), 1224−1231. (15) Mitch, W. A.; Schreiber, I. M. Degradation of tertiary alkylamines during chlorination/chloramination: Implications for formation of aldehydes, nitriles, halonitroalkanes, and nitrosamines. Environ. Sci. Technol. 2008, 42 (13), 4811−4817. (16) Le Roux, J.; Gallard, H.; Croué, J.-P. Formation of NDMA and halogenated DBPs by chloramination of tertiary amines: The influence of bromide ion. Environ. Sci. Technol. 2012, 46 (3), 1581−1589. (17) Selbes, M.; Kim, D.; Ates, N.; Karanfil, T. The roles of tertiary amine structure, background organic matter and chloramine species on NDMA formation. Water Res. 2013, 47 (2), 945−953. (18) Shen, R.; Andrews, S. A. Demonstration of 20 pharmaceuticals and personal care products (PPCPs) as nitrosamine precursors during chloramine disinfection. Water Res. 2011, 45 (2), 944−952. (19) Chen, W. H.; Young, T. M. NDMA formation during chlorination and chloramination of aqueous diuron solutions. Environ. Sci. Technol. 2008, 42 (4), 1072−1077. (20) Mitch, W. A.; Sedlak, D. L. Characterization and fate of Nnitrosodimethylamine precursors in municipal wastewater treatment plants. Environ. Sci. Technol. 2004, 38 (5), 1445−1454.
loadings of NDMA and its chloramine- and ozone-reactive precursors. Wastewater effluents were also important contributors of TONO and its chloramine- and ozone-reactive precursors. Algal blooms also may be significant for TONO when a major fraction of the water supply is affected, but a very high fraction of the water supply would need to derive from agricultural or stormwater runoff for their loadings to be important. In addition to hydrologic modeling, future research is needed to evaluate the natural attenuation of precursor pools in source waters prior to reaching drinking water supplies.62−64
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ASSOCIATED CONTENT
* Supporting Information S
This material is free of charge via the Internet at The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.6b04650. Additional experimental details, tables, and figures as noted in the text (PDF)
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AUTHOR INFORMATION
Corresponding Authors
*(W.A.M.) Phone: 650-725-9298; fax: 650-723-7058; e-mail:
[email protected]. *(E.R.V.) Phone: 702-856-3668; fax: 702-856-3647; e-mail:
[email protected]. ORCID
William A. Mitch: 0000-0002-4917-0938 Author Contributions ∇
C.M.G. and T.Z. contributed equally to this work.
Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS We gratefully acknowledge project partners and participating utilities for assistance of sample collection. This research was supported by the Water Research Foundation (Project 4591) and the National Science Foundation Engineering Research Center for Re-Inventing the Nation’s Urban Water Infrastructure (ReNUWIt). We would also like to acknowledge the SNWA’s Analytical Research and Development group including Dr. Eric Wert for project support, Rebecca Trenholm for the analysis of N-nitrosamines, Oscar Quinones for the analysis of sucralose, Brett Vanderford for data review, Janie Ziegler, Derek Pattinson, Brittney Stipanov, and Brianna Enright for sample preparation and extraction, and Amanda Jacob and Charles Vasconcelos Da Silva for assistance with sample collection and preparation. TZ acknowledges the support of 2016 Syracuse Center of Excellence (SyracuseCoE) Faculty Fellows Program. The information, data, or work presented herein was funded in part by an award from New York State Department of Economic Development (DED), through the Syracuse Center of Excellence, under Award Number #C150183. Any opinions, findings, conclusions or recommendations expressed are those of the author(s) and do not necessarily reflect the views of the DED.
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REFERENCES
(1) National Research Council, Water Reuse: Potential for Expanding the Nation’s Water Supply Through Reuse of Municipal Wastewater. The National Academies Press: Washington, DC, 2012; p 262. 13246
DOI: 10.1021/acs.est.6b04650 Environ. Sci. Technol. 2016, 50, 13239−13248
Article
Environmental Science & Technology (21) Kosaka, K.; Asami, M.; Konno, Y.; Oya, M.; Kunikane, S. Identification of antiyellowing agents as precursors of N-nitrosodimethylamine production on ozonation from sewage treatment plant influent. Environ. Sci. Technol. 2009, 43 (14), 5236−5241. (22) Kosaka, K.; Asami, M.; Ohkubo, K.; Iwamoto, T.; Tanaka, Y.; Koshino, H.; Echigo, S.; Akiba, M. Identification of a new Nnitrosodimethylamine precursor in sewage containing industrial effluents. Environ. Sci. Technol. 2014, 48 (19), 11243−11250. (23) Marti, E. J.; Pisarenko, A. N.; Peller, J. R.; Dickenson, E. R. V. NNitrosodimethylamine (NDMA) formation from the ozonation of model compounds. Water Res. 2015, 72, 262−270. (24) Schmidt, C. K.; Brauch, H. J. N,N-Dimethosulfamide as precursor for N-nitrosodimethylamine (NDMA) formation upon ozonation and its fate during drinking water treatment. Environ. Sci. Technol. 2008, 42 (17), 6340−6346. (25) Park, S. H.; Wei, S.; Mizaikoff, B.; Taylor, A. E.; Favero, C.; Huang, C. H. Degradation of amine-based water treatment polymers during chloramination as N-nitrosodimethylamine (NDMA) precursors. Environ. Sci. Technol. 2009, 43 (5), 1360−1366. (26) Kemper, J. M.; Westerhoff, P.; Dotson, A.; Mitch, W. A. Nitrosamine, dimethylnitramine, and chloropicrin formation during strong base anion-exchange treatment. Environ. Sci. Technol. 2009, 43 (2), 466−472. (27) Flowers, R. C.; Singer, P. C. Anion exchange resins as a source of nitrosamines and nitrosamine precursors. Environ. Sci. Technol. 2013, 47 (13), 7365−7372. (28) Hanigan, D.; Thurman, E. M.; Ferrer, I.; Zhao, Y.; Andrews, S.; Zhang, J.; Herckes, P.; Westerhoff, P. Methadone contributes to Nnitrosodimethylamine formation in surface wters and wastewaters during chloramination. Environ. Sci. Technol. Lett. 2015, 2 (6), 151− 157. (29) Dai, N.; Mitch, W. A. Relative importance of N-nitrosodimethylamine compared to total N-nitrosamines in drinking waters. Environ. Sci. Technol. 2013, 47 (8), 3648−3656. (30) Dai, N.; Zeng, T.; Mitch, W. A. Predicting N-nitrosamines: NNitrosodiethanolamine as a significant component of total Nnitrosamines in recycled wastewater. Environ. Sci. Technol. Lett. 2015, 2 (3), 54−58. (31) Gerecke, A. C.; Sedlak, D. L. Precursors of N-nitrosodimethylamine in natural waters. Environ. Sci. Technol. 2003, 37 (7), 1331− 1336. (32) Mitch, W. A.; Krasner, S. W.; Westerhoff, P.; Dotson, A. Occurrence and Formation of Nitrogenous Disinfection By-Products; Water Research Foundation, Report 91250; Denver, CO, 2009. (33) Wert, E. C.; Rosario-Ortiz, F. L. Intracellular organic matter from cyanobacteria as a precursor for carbonaceous and nitrogenous disinfection byproducts. Environ. Sci. Technol. 2013, 47 (12), 6332− 6340. (34) Krasner, S. W.; Westerhoff, P.; Chen, B.; Rittmann, B. E.; Amy, G. Occurrence of disinfection byproducts in United States wastewater treatment plant effluents. Environ. Sci. Technol. 2009, 43 (21), 8320− 8325. (35) Lawaetz, A. J.; Stedmon, C. A. Fluorescence intensity calibration using the Raman scatter peak of water. Appl. Spectrosc. 2009, 63 (8), 936−940. (36) Cory, R. M.; Miller, M. P.; McKnight, D. M.; Guerard, J. J.; Miller, P. L. Effect of instrument-specific response on the analysis of fulvic acid fluorescence spectra. Limnol. Oceanogr.: Methods 2010, 8 (2), 67−78. (37) Zeng, T.; Mitch, W. A. Contribution of N-nitrosamines and their precursors to domestic sewage by greywaters and blackwaters. Environ. Sci. Technol. 2015, 49 (22), 13158−13167. (38) Shah, A. D.; Krasner, S. W.; Lee, C. F. T.; von Gunten, U.; Mitch, W. A. Trade-offs in disinfection byproduct formation associated with precursor preoxidation for control of N-nitrosodimethylamine formation. Environ. Sci. Technol. 2012, 46 (9), 4809−4818. (39) Hollender, J.; Zimmermann, S. G.; Koepke, S.; Krauss, M.; McArdell, C. S.; Ort, C.; Singer, H.; von Gunten, U.; Siegrist, H. Elimination of organic micropollutants in a municipal wastewater
treatment plant upgraded with a full-scale post-ozonation followed by sand filtration. Environ. Sci. Technol. 2009, 43 (20), 7862−7869. (40) Zimmermann, S. G.; Wittenwiler, M.; Hollender, J.; Krauss, M.; Ort, C.; Siegrist, H.; von Gunten, U. Kinetic assessment and modeling of an ozonation step for full-scale municipal wastewater treatment: Micropollutant oxidation, by-product formation and disinfection. Water Res. 2011, 45 (2), 605−617. (41) Lee, Y.; Gerrity, D.; Lee, M.; Bogeat, A. E.; Salhi, E.; Gamage, S.; Trenholm, R. A.; Wert, E. C.; Snyder, S. A.; von Gunten, U. Prediction of micropollutant elimination during ozonation of municipal wastewater effluents: Use of kinetic and water specific information. Environ. Sci. Technol. 2013, 47 (11), 5872−5881. (42) Antoniou, M. G.; Hey, G.; Rodríguez Vega, S.; Spiliotopoulou, A.; Fick, J.; Tysklind, M.; la Cour Jansen, J.; Andersen, H. R. Required ozone doses for removing pharmaceuticals from wastewater effluents. Sci. Total Environ. 2013, 456−457, 42−49. (43) Kovalova, L.; Siegrist, H.; von Gunten, U.; Eugster, J.; Hagenbuch, M.; Wittmer, A.; Moser, R.; McArdell, C. S. Elimination of micropollutants during post-treatment of hospital wastewater with powdered activated carbon, ozone, and UV. Environ. Sci. Technol. 2013, 47 (14), 7899−7908. (44) Sgroi, M.; Roccaro, P.; Oelker, G. L.; Snyder, S. A. NNitrosodimethylamine formation upon ozonation and identification of precursors source in a municipal wastewater treatment plant. Environ. Sci. Technol. 2014, 48 (17), 10308−10315. (45) Holady, J. C.; Trenholm, R. A.; Snyder, S. A. Use of automated solid-phase extraction and GC-MS/MS to evaluate nitrosamines in water matrices. Am. Lab. 2012, 44 (3), 6. (46) Kulshrestha, P.; McKinstry, K. C.; Fernandez, B. O.; Feelisch, M.; Mitch, W. A. Application of an optimized total N-nitrosamine (TONO) assay to pools: Placing N-nitrosodimethylamine (NDMA) determinations into perspective. Environ. Sci. Technol. 2010, 44 (9), 3369−3375. (47) Oppenheimer, J.; Eaton, A.; Badruzzaman, M.; Haghani, A. W.; Jacangelo, J. G. Occurrence and suitability of sucralose as an indicator compound of wastewater loading to surface waters in urbanized regions. Water Res. 2011, 45 (13), 4019−4027. (48) Lange, F. T.; Scheurer, M.; Brauch, H.-J. Artificial sweeteners−A recently recognized class of emerging environmental contaminants: A review. Anal. Bioanal. Chem. 2012, 403 (9), 2503−2518. (49) Mawhinney, D. B.; Young, R. B.; Vanderford, B. J.; Borch, T.; Snyder, S. A. Artificial sweetener sucralose in U.S. drinking water systems. Environ. Sci. Technol. 2011, 45 (20), 8716−8722. (50) Kristiana, I.; Tan, J.; Joll, C. A.; Heitz, A.; von Gunten, U.; Charrois, J. W. A. Formation of N-nitrosamines from chlorination and chloramination of molecular weight fractions of natural organic matter. Water Res. 2013, 47 (2), 535−546. (51) Elespuru, R. K.; Lijinsky, W. The formation of carcinogenic nitroso compounds from nitrite and some types of agricultural chemicals. Food Cosmet. Toxicol. 1973, 11 (5), 807−817. (52) Khan, S. U.; Young, J. C. N-Nitrosamine formation in soil from the herbicide glyphosate. J. Agric. Food Chem. 1977, 25 (6), 1430− 1432. (53) Pancholy, S. K. Formation of carcinogenic nitrosamines in soils. Soil Biol. Biochem. 1978, 10 (1), 27−32. (54) Yang, W. C.; Gan, J.; Liu, W. P.; Green, R. Degradation of Nnitrosodimethylamine (NDMA) in landscape soils. J. Environ. Qual. 2005, 34 (1), 336−341. (55) Arienzo, M.; Gan, J.; Ernst, F.; Qin, S.; Bondarenko, S.; Sedlak, D. L. Loss pathways of N-nitrosodimethylamine (NDMA) in turfgrass soils. J. Environ. Qual. 2006, 35 (1), 285−292. (56) Gan, J.; Bondarenko, S.; Ernst, F.; Yang, W.; Ries, S. B.; Sedlak, D. L. Leaching of N-nitrosodimethylamine (NDMA) in turfgrass soils during wastewater irrigation. J. Environ. Qual. 2006, 35 (1), 277−284. (57) Leavey-Roback, S. L.; Krasner, S. W.; Suffet, I. H. Veterinary antibiotics used in animal agriculture as NDMA precursors. Chemosphere 2016, 164, 330−338. (58) Shaw, S. L.; Mitloehner, F. M.; Jackson, W.; DePeters, E. J.; Fadel, J. G.; Robinson, P. H.; Holzinger, R.; Goldstein, A. H. Volatile 13247
DOI: 10.1021/acs.est.6b04650 Environ. Sci. Technol. 2016, 50, 13239−13248
Article
Environmental Science & Technology organic compound emissions from dairy cows and their waste as measured by proton-transfer-reaction mass spectrometry. Environ. Sci. Technol. 2007, 41 (4), 1310−1316. (59) Mosier, A. R.; Torbit, S. Synthesis and stability of dimethylnitrosamine in cattle manure. J. Environ. Qual. 1976, 5 (4), 465−468. (60) U.S. Geological Survey Current Conditions for Nevada: Streamflow; U.S. Geological Survey: Reston, VA, 2015. http:// waterdata.usgs.gov/nv/nwis/current/?type=flow (accessed November 1, 2016). (61) Selbes, M.; Yilmaz, O.; Khan, A. A.; Karanfil, T. Leaching of DOC, DN, and inorganic constituents from scrap tires. Chemosphere 2015, 139, 617−623. (62) Schreiber, I. M.; Mitch, W. A. Occurrence and fate of nitrosamines and nitrosamine precursors in wastewater-impacted surface waters using boron as a conservative tracer. Environ. Sci. Technol. 2006, 40 (10), 3203−3210. (63) Plumlee, M. H.; Reinhard, M. Photochemical attenuation of Nnitrosodimethylamine (NDMA) and other nitrosamines in surface water. Environ. Sci. Technol. 2007, 41 (17), 6170−6176. (64) Woods, G. C.; Dickenson, E. R. V. Natural attenuation of NDMA precursors in an urban, wastewater-dominated wash. Water Res. 2016, 89, 293−300.
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